1. Field of the Invention
The present invention relates generally to a magnetic disk drive, and more particularly to a stopper mechanism for restricting the range of rotational movement of a head actuator in the magnetic disk drive.
2. Description of the Related Art
In a magnetic disk drive, a magnetic head is mounted at the tip of a head actuator to read/write data on a data zone of a magnetic disk rotating at high speeds. An actuator stopper is provided in the magnetic disk drive to restrict the range of rotational movement of a rotary head actuator. In the event that the head actuator runs away for any one of a number reasons, the actuator stopper serves to prevent the magnetic head mounted at the tip of the head actuator from being deflected from the magnetic disk. The actuator stopper serves also to define a start position of servo track writing.
In a conventional actuator stopper mechanism in a magnetic disk drive, an inner stopper and an outer stopper are bonded to or press-fitted with a magnetic circuit fixed to a base of the magnetic disk drive, and a coil supporting portion of a head actuator is formed so as to come into contact with either the inner stopper or the outer stopper, thereby restricting the range of rotational movement of the head actuator.
In general, each of the inner stopper and the outer stopper includes a shaft and a cylindrical rubber cushion mounted on the shaft. The cylindrical rubber cushion functions to reduce the impact acceleration of the head actuator upon collision of the head actuator against the inner stopper or the outer stopper in case of running-away of the head actuator, thereby preventing damage to the disk from the head mounted on the head actuator striking against the disk.
In the case that the head actuator runs away, the impact acceleration in a seek direction of the head actuator is large. Accordingly, the rubber cushion in the conventional stopper mechanism has a low rubber hardness to suppress the impact acceleration. In general, however, the rubber cushion having a low rubber hardness is higher in cost than a rubber cushion having a high rubber hardness.
Another know type of actuator stopper mechanism is one having a structure in which a rubber cushion like an O-ring is press-fitted with a shaft. In this structure, a striking position of the head actuator on the O-ring may slip because of by variations in the vertical tolerance of the head actuator, causing variations in the start position of servo track writing. Further, a possible slip in of position of the O-ring causes an increase in vertical acceleration of the head actuator when it runs away. Additionally, the use of such an O-ring shaped rubber cushion requires a complicated mold, causing an increase in cost of the mold.